---
layout: example
category: example
title: Create a time slider
description: Drag the range slider to visualize earthquakes that were greater than 5.9 magnitude in 2015.
tags:
  - user-interaction
  - sources
---
<style>
.map-overlay {
    font: 12px/20px 'Helvetica Neue', Arial, Helvetica, sans-serif;
    position: absolute;
    width: 25%;
    top: 0;
    left: 0;
    padding: 10px;
}

.map-overlay .map-overlay-inner {
    background-color: #fff;
    box-shadow:0 1px 2px rgba(0, 0, 0, 0.20);
    border-radius: 3px;
    padding: 10px;
    margin-bottom: 10px;
}

.map-overlay h2 {
    line-height: 24px;
    display: block;
    margin: 0 0 10px;
}

.map-overlay .legend .bar {
    height: 10px;
    width: 100%;
    background: linear-gradient(to right, #FCA107, #7F3121);
}

.map-overlay input {
    background-color: transparent;
    display: inline-block;
    width: 100%;
    position: relative;
    margin: 0;
    cursor: ew-resize;
}
</style>

<div id='map'></div>

<div class='map-overlay top'>
    <div class='map-overlay-inner'>
        <h2>Significant earthquakes in 2015</h2>
        <label id='month'></label>
        <input id='slider' type='range' min='0' max='11' step='1' value='0' />
    </div>
    <div class='map-overlay-inner'>
        <div id='legend' class='legend'>
            <div class='bar'></div>
            <div>Magnitude (m)</div>
        </div>
    </div>
</div>

<script src='//d3js.org/d3.v3.min.js' charset='utf-8'></script>
<script>
var map = new mapboxgl.Map({
    container: 'map',
    style: 'mapbox://styles/mapbox/light-v9',
    center: [31.4606, 20.7927],
    zoom: 0.5
});

var months = [
    'January',
    'February',
    'March',
    'April',
    'May',
    'June',
    'July',
    'August',
    'September',
    'October',
    'November',
    'December'
];

function filterBy(month) {

    var filters = ['==', 'month', month];
    map.setFilter('earthquake-circles', filters);
    map.setFilter('earthquake-labels', filters);

    // Set the label to the month
    document.getElementById('month').textContent = months[month];
}

map.on('load', function() {

    // Data courtesy of http://earthquake.usgs.gov/
    // Query for significant earthquakes in 2015 URL request looked like this:
    // http://earthquake.usgs.gov/fdsnws/event/1/query
    //    ?format=geojson
    //    &starttime=2015-01-01
    //    &endtime=2015-12-31
    //    &minmagnitude=6'
    //
    // Here we're using d3 to help us make the ajax request but you can use
    // Any request method (library or otherwise) you wish.
    d3.json('{{site.baseurl}}/assets/data/significant-earthquakes-2015.geojson', function(err, data) {
        if (err) throw err;

        // Create a month property value based on time
        // used to filter against.
        data.features = data.features.map(function(d) {
            d.properties.month = new Date(d.properties.time).getMonth();
            return d;
        });

        map.addSource('earthquakes', {
            'type': 'geojson',
            'data': data
        });

        map.addLayer({
            'id': 'earthquake-circles',
            'type': 'circle',
            'source': 'earthquakes',
            'paint': {
                'circle-color': {
                    property: 'mag',
                    stops: [
                        [6, '#FCA107'],
                        [8, '#7F3121']
                    ]
                },
                'circle-opacity': 0.75,
                'circle-radius': {
                    property: 'mag',
                    stops: [
                        [6, 20],
                        [8, 40]
                    ]
                }
            }
        });

        map.addLayer({
            'id': 'earthquake-labels',
            'type': 'symbol',
            'source': 'earthquakes',
            'layout': {
                'text-field': '{mag}m',
                'text-font': ['Open Sans Bold', 'Arial Unicode MS Bold'],
                'text-size': 12
            },
            'paint': {
                'text-color': 'rgba(0,0,0,0.5)'
            }
        });

        // Set filter to first month of the year
        // 0 = January
        filterBy(0);

        document.getElementById('slider').addEventListener('input', function(e) {
            var month = parseInt(e.target.value, 10);
            filterBy(month);
        });
    });
});
</script>
